This invention concerns image producing apparatus, and particularly but not exclusively such apparatus usable in surgery, and especially neurosurgery.
Computer assisted surgery is an important tool for minimally invasive procedures. It allows for planning procedures before an operation, and is usually based upon a three dimensional image of the anatomy produced beforehand, for instance by magnetic resonance imaging. However, where the anatomical substrate is soft and affected by a patients position during surgery, the initial images obtained are of limited use as organs in the body will have moved. This is particularly the position in neurosurgery where for instance it may be required to remove a tumour, but where it is highly significant not to remove surrounding live tissue.
According to the present invention there is provided image producing apparatus, the apparatus comprising means for producing and also receiving an ultrasound signal, the apparatus being arranged such that a plurality of ultrasound signals are sequentially produced in different directions, the apparatus also comprising means for analysing the ultrasound signals produced and received so as to produce a three dimensional image therefrom.
The apparatus preferably comprises a single ultrasound signal producing and receiving means, which may comprise a piezo element.
The apparatus may comprise a reflecting mirror for reflecting the ultrasound signals. The reflecting mirror may be movable within the apparatus. The reflecting mirror may be rotationally movable, and may also be linearly movable. The ultrasound signal producing and receiving means and reflecting mirror are preferably maintained in a constant spaced relationship with the apparatus.
In one embodiment the ultrasound signal producing and receiving means is movable within the apparatus. The ultrasound signal producing and receiving means may be linearly movable.
The ultrasound signal producing and receiving means, and reflecting mirror, are preferably provided respectively on first and second movable concentric cylindrical members, which members are rotatable relative to each other. A one of the cylindrical members preferably extends at least partially within the other. The ultrasound signal producing and receiving means may be provided on the inner cylindrical member.
The reflecting mirror is preferably movable in a generally helical path.
The two cylindrical members are preferably movable by a common rotational drive. The cylindrical member bearing the ultrasound signal producing and receiving means may engage with a helically threaded member rotatable by the common drive, with means preventing rotation of said cylindrical member. The cylindrical member bearing the reflecting mirror may rotatably engage with an elongate gear rotatable by the common drive. Said cylindrical member bearing the reflecting mirror may be linearly movable by the other cylindrical member.
The apparatus may be arranged to produce an image of a substantially cylindrical volume.
In an alternative arrangement a second mirror may be provided for reflecting the ultrasound signals downstream of the reflecting mirror. The second mirror may be pivotally movable relative to the reflecting mirror and may be pivotal by virtue of a cam arrangement. The apparatus may be arranged to produce an image of a substantially frusto conical volume.
The apparatus preferably comprises a housing which locates the ultrasound producing and receiving means, and means for moving same. A part of the housing is preferably liquid tight such that an ultrasound liquid couplant can be contained therein.
The apparatus preferably comprises a motor for moving the movable parts of the apparatus. The motor which may be a d.c. motor, is preferably located outside of the liquid tight part of the housing.
The apparatus preferably comprises means for detecting the position of the ultrasound signal producing and receiving means relative to at least said receiving mirror, said detecting means being operatively connected to the analysing means. One or more position sensors may be provided, and the sensors may comprise inductive switches. The sensors may detect both linear and rotational movement, and an inductive switch may be provided to detect linear movement. An inductive switch which detects the relative rotational position of a member rotatable by the common drive may also be provided.
The housing may comprise a projecting part which is significantly narrower than the remainder of the housing, and which projecting part locates the ultrasound signal producing and receiving means.
The analysing means may convert signals received from the ultrasound signal producing and receiving means from analogue to digital signals. The analysing means may be arranged such that once a three dimensional image has been produced, this image is automatically updated by further signals received.